The present invention concerns a multilayer circuit board which can be appropriately used in high-frequency, electric signal transmission equipment such as electronic equipment, communications equipment and electronic computers.
One of the present applicants, Satoru Kobayashi, has been involved in the development of high-frequency circuit boards, and has proposed a multilayer circuit board which prevents an increase in signal propagation lag time by using a porous material for a dielectric which is inserted between adjacent printed circuit boards, disclosed in Japanese Utility Model Nos. 62-49,277 and 62-65,879 (which correspond to U.S. Pat. No. 4,755,911).
Conventionally, circuit boards which use a porous material as a substrate have been superior in terms of electrical characteristics such as propagation lag time. In such cases, however, because the substrate itself is soft and spongy, the circuit board has little resistance to bending stress when a multilayer arrangement is formed. Thus, such circuit boards have been considered inappropriate for use in multilayer configurations.
The present invention was designed in light of the abovementioned drawbacks encountered in the prior art. The object of the present invention is to provide a multilayer circuit board which is superior in terms of electrical characteristics such as propagation lag time, and which is also superior in terms of mechanical strength characteristics.